Is Cranberry Useful in Preventing Recurrent Urinary Tract Infections?

Cranberry capsules aren’t as effective as trimethoprim-sulfamethoxazole (TMP-SMX) in preventing recurrent urinary tract infections (UTIs), but TMP-SMX is associated with high rates of emerging antibiotic resistance, concludes a trial published in the Archives of Internal Medicine.

The randomized trial included 221 premenopausal women with a history of recurrent UTIs: at least three symptomatic infections in the previous year. In double-blind, double-dummy fashion, patients were assigned to receive prophylactic TMP-SMX 480 mg once daily, or cranberry capsules 500 mg twice daily. Over 1 year of treatment, the rates and numbers of symptomatic UTIs were compared between groups. The development of antibiotic resistance in native Escherichia coli was monitored as well.

During the study year, patients taking cranberry capsules had about twice as many infections as those taking antibiotics: 4.0 versus 1.8. At least one infection occurred in 78.2 percent versus 71.1 percent of patients; the median time to initial recurrence was 4 versus 8 months, respectively.

However, prophylactic TMP-SMX was associated with high rates of antibiotic resistance. Fecal E. coli isolates resistant to TMP-SMX were found at 1 month in 86.3 percent of the antibiotic group versus 23.7 percent of the cranberry group. Patients taking antibiotics also had higher rates of asymptomatic bacteriuria E. coli isolates as well as increased rates of trimethoprim, amoxicillin, and ciprofloxacin resistance. The differences in antibiotic resistance resolved 3 months after discontinuation of TMP-SMX.

Prophylactic antibiotics are widely used for prevention of recurrent UTIs. However, problems with antibiotic resistance have led to renewed interest in the potential for cranberry to reduce recurrent UTI risk.

The new trial found a lower rate of recurrent UTIs with prophylactic TMP-SMX than with cranberry capsules. However, this benefit of TMP-SMX was accompanied by high rates of antibiotic resistance. A formal cost-utility analysis of these two alternatives is planned [Beerepoot MAJ, et al. Cranberries vs. antibiotics to prevent urinary tract infections: a randomized double-blind noninferiority trial in premenopausal women. Arch Intern Med 2011; 171:1270–1278].